One person can randomly fire up the grill on a tuesday, sure, but big BBQs with various friends invited tend to be on weekends... i'm not american but we also follow this "rule".If it's a big social BBQ then the weekend would make much more sense. But it does suggest that someone at the BBQ is important for moving the plot forward if it needs to happen now. Santi's most obvious, maybe an opportunity to talk to Adriana and get out of the suspension? Both of those feel like they shouldn't only happen on Alexis / Layla routes though...
Exceptions for holydays or if everybody has a day off.
It becomes somewhat dodgy in terms of plot relevance if it's an optional scene.
And it is optional, the Valeria party is also scheduled for the same exact time.
Nyx even planned a 3rd scene(movies) if you didn't meet the criteria for invitation.
Some friends do get invited, Layla invited Elena and i think she said Alexis was going to invite Erynn.Why would you be invited to a family BBQ if you aren't?
But i don't think the MC is quite at this level of friendship, Layla doesn't say anything about a BBQ if you aren't dating her or Alexis.